Add flake

Signed-off-by: Nikolaos Karaolidis <nick@karaolidis.com>

flake.nix

@@ -0,0 +1,33 @@
+{
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+
+    flake-utils.url = "github:numtide/flake-utils";
+
+    treefmt-nix = {
+      url = "github:numtide/treefmt-nix";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
+  };
+
+  outputs =
+    inputs:
+    (
+      let
+        system = "x86_64-linux";
+
+        pkgs = import inputs.nixpkgs {
+          inherit system;
+          config.allowUnfree = true;
+        };
+
+        treefmt = inputs.treefmt-nix.lib.evalModule pkgs ./treefmt.nix;
+      in
+      {
+        devShells.${system}.default = pkgs.mkShell { packages = with pkgs; [ hugo ]; };
+
+        formatter.${system} = treefmt.config.build.wrapper;
+        checks.formatting.${system} = treefmt.config.build.check inputs.self;
+      }
+    );
+}